PC board fluidic devices

ABSTRACT

PC board fluidic devices for performing a Polymerase Chain Reaction (PCR) are disclosed. The devices comprise a printed circuit board and a PCR chamber. The PCR chamber is a fluidic chamber and is located in, or is part of, the PC board. The PC board can include a coil trace heating element with a temperature sensor and controller.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Divisional of U.S. application Ser. No.13/763,352 filed on Feb. 8, 2013, which, in turn, claims priority toU.S. provisional application 61/597,554 for “PC Board-based PolymeraseChain Reaction System, Methods and Materials” filed on Feb. 10, 2012,both of which are herein incorporated by reference in their entirety.

FIELD

The present disclosure relates to PC board fluidic devices, suchapparatuses for performing a Polymerase Chain Reaction (PCR), methodsfor manufacturing apparatuses for performing a Polymerase Chain Reaction(PCR) and methods for performing a Polymerase Chain Reaction (PCR).

BACKGROUND

Polymerase chain reaction (PCR) is one of the cornerstones of modernbiology, as it permits for the amplification of specific sequences ofDNA from naturally occurring concentrations to concentrations detectableby other molecular biology techniques. In addition to the widespread useof polymerase chain reaction (PCR) as a technique in laboratories, it isalso extensively used in medicine as a gold standard for the detectionof infectious pathogens.

SUMMARY

According to a first aspect of the present disclosure, an apparatus forperforming a Polymerase Chain Reaction (PCR) is provided, the apparatuscomprising a PCR chamber for performing a Polymerase Chain Reaction anda printed circuit board (PCB) fluidic device, wherein the PCR chamber isa fluidic chamber and is located in, or is part of, the printed circuitboard (PCB) fluidic device.

According to a second aspect of the present disclosure, a method formanufacturing an apparatus for performing Polymerase Chain Reaction(PCR) is provided, the method including the step of manufacturing theapparatus for performing PCR using a printed circuit board (PCB)fluidics fabrication process.

According to a third aspect of the disclosure, a method for performing aPolymerase Chain Reaction (PCR) is provided, the method comprisingperforming a PCR in a PCR chamber, wherein the PCR chamber is a fluidicchamber part of a printed circuit board (PCB) fluidic device.

According to a fourth aspect of the disclosure, a printed circuit board(PCB) fluidic device is presented, the printed circuit board (PCB)fluidic device including a Polymerase Chain Reaction (PCR) chamber forperforming a PCR.

Further aspects of the disclosure are shown in the specification,drawings and claims of the present application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a view of an apparatus layout according to some embodimentsof the present disclosure, comprising a heater coil layer and a chamberlayer.

FIG. 2 shows the heater coil layer only of the apparatus of FIG. 1.

FIG. 3 shows a schematic cross sectional view of the apparatus of FIG.1.

FIG. 4 shows a schematic cross sectional view of the apparatus of FIG.1, wherein a rigid printed circuit board layer is added.

FIG. 5 shows a schematic cross sectional view of an apparatus accordingto some embodiments of the present disclosure, wherein a temperaturesensor is bonded on top of the chamber layer.

FIG. 6 shows a schematic cross sectional view of an apparatus accordingto some embodiments of the present disclosure, wherein a temperaturesensor is bonded on the bottom of the chamber layer.

FIG. 7 shows an exemplary cooling method for a chamber according to someembodiments of the present disclosure.

FIG. 8 shows an exemplary diagram of a printed circuit board (PCB) basedPolymerase Chain Reaction System according to some embodiments of thepresent disclosure.

FIG. 9 shows a block diagram of a controller for an apparatus accordingto some embodiments of the present disclosure.

FIG. 10 shows preliminary heating and cooling curves for a controller ofan apparatus according to some embodiments of the present disclosure.

FIG. 11 shows a schematic diagram of a part of a controller for anapparatus according to some embodiments of the present disclosure.

FIG. 12 shows a schematic diagram of a further part of a controller foran apparatus according to some embodiments of the present disclosure.

FIG. 13 shows a schematic diagram of a further part of a controller foran apparatus according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

PCR is a fairly complex procedure to implement, which has limited itsuse in the context of point-of-care medicine. In fact, in PCR, a targetDNA sequence is typically mixed with a DNA polymerase enzyme, DNA basepairs, DNA primers with base pairs corresponding to the beginning andend of the target DNA sequence, and a variety of other reagents toimprove the performance of the procedure.

In addition to the complexity of the reagents involved, the actualexecution of the procedure can require a sample to be thermally cycledamong several different temperatures. These temperature steps typicallycan involve a denaturation step, where a double-stranded DNA molecule tobe copied is split into two single-stranded DNA molecules (typically inthe 94-96C range); an annealing step, where the DNA primers bind to thetarget sequence on the single-stranded DNA molecules (50-65C range); andan extension step, where the DNA polymerase enzyme makes a copy of thesingle stranded DNA molecules beginning from each DNA primer, producingdouble stranded DNA molecules and doubling the concentration of thetarget DNA sequence.

Current commercial systems for performing this thermal cycling, havetypically been large, bulky benchtop devices which use expensive Peltierjunction devices to quickly heat and cool samples.

Based on the above recognitions and observations of the inventors, withreference to the attached drawings and according to some embodiments ofthe present disclosure, a PCR system based on printed circuit board(PCB) fluidic device is disclosed.

According to some aspects of the present disclosure, FIG. 1 shows anapparatus for performing a Polymerase Chain Reaction (PCR) which cancomprise a PCR chamber (15) for performing a Polymerase Chain Reactionplaced in a printed circuit board (PCB) fluidic device (100). The PCRchamber is a fluidic chamber (15) and is located in, or is part of, theprinted circuit board (PCB) fluidic device (100). It follows that thePolymerase Chain Reaction described here above can be performed in theprinted circuit board (PCB) fluidic device (100). The term “printedcircuit board (PCB) fluidic device (100)” can be meant as a chipstructure provided with ports and channels suitable for passage offluid. In particular, reactants of Polymerase Chain Reaction can be fedin fluidic channels and/or ports (17) of the printed circuit board (PCB)fluidic device (100) to react in the PCR chamber (15). It furtherfollows that a PCR chamber is part of, or is embedded in, or isintegrated with, the layers of a printed circuit board (PCB) fluidicdevice (100).

According to some aspects of the present disclosure, PCB fluidics canpermit, for example, the integration of both fluidic and electronicsystems on the same board with a few modifications to the standard PCBfabrication process.

Due to the current maturity of the PCB fabrication process and theubiquity of PCBs, both per-unit manufacturing costs and one-time costs(tooling, NRE) can be exceptionally low, and turnaround time can beshort. These factors can make the apparatus according of the presentdisclosure particularly attractive for integration into point-of-carepathogen identification systems which could permit patients, possiblyeven in the developing world, to very quickly find out whether or notthey are infected with HIV, tuberculosis, or other pathogens.

With reference to FIG. 1 and FIG. 3, according to some embodiments ofthe present disclosure, a PCR chamber (15) of dimensions appropriate forthe required reaction (typically in the microliter range) can be formedusing multilayer PCB fluidics fabrication methods.

The apparatus can include a multilayer flex-on-rigid backing design withflex layers (16), wherein the PCR chamber (15) can be contained withinthe flex layers (16). In some embodiments of the present disclosure thePCR chamber is contained entirely within the flex layers (16). Thechamber can be etched out from the flex layers. It follows that,according to some embodiments of the present disclosure, the entireapparatus can be a multilayer flex-on-rigid backing design.

According to further aspects of the present disclosure, the apparatuscan be composed of materials compatible with the PCR reaction. Forexample looking at FIG. 3, the flex layers (16) can be made of Kaptoncompatible with the polymerase chain reaction. The person skilled in theart will know that Kapton is a polyimide and as such has good thermalstability, good chemical resistance and excellent mechanical properties.

As shown in FIG. 4, a basement (18) can be further located beneath theflex layers (16), wherein the basement (18) may contain electroniccircuit board traces (22) as well as some electronic devices as shownfor example in FIG. 12. The basement can further contain a heater (23)for heating the PCR chamber. The basement can be a FR-4 basedconstruction, which is a rigid fiberglass/composite sheet commonly usedto fabricate rigid printed circuit boards. Although FR-4 material is notbiocompatible with PCR, in this embodiment it is used in a layer thatcan be not in contact with the reagents which may adversely impactoperation of electronic components included within the FR-4 layer. Itfollows that according to further aspects of the present disclosure, theprinted circuit board (PCB) fluidic device (100) can be designed andconfigured to include both the PCR chamber and the traces andelectronics device. In fact, the PCR chamber and the traces andelectronics device can be located in different layers of the printedcircuit board (PCB) fluidic device (100).

According to some aspects of the present disclosure, the heater (23) forheating the PCR chamber (15) can be a coil trace, for example a coppercoil trace, located beneath the PCR chamber for heating reactants of thepolymerase chain reaction. As it shown in FIG. 3, the coil trace can beindirectly connected, without any direct connection, to the chamber(15). More in particular and as shown in FIG. 1 and FIG. 2, the coiltrace can be a long, thin coil trace beneath the PCR chamber (15) forheating the sample via controlled current flow within the coil. The coiltrace may be etched within a flex layer underneath the chamber, asdepicted in FIG. 3, or alternatively, it may be etched within a rigidFR-4 layer and also placed underneath the chamber. As a consequence, thechip substrate may be all polyimide or a hybrid polyimide/FR-4.

According to some embodiments of the present disclosure a cooler (e.g.fan (24) in FIG. 7) can be provided to cool down the chamber whenrequired. In particular, cooling can be accomplished either passively(e.g. stopping the heating process), or actively, for example withforced convection through a fan (24), as all of the temperaturesrequired for PCR can be above room temperature. As shown in FIG. 7, thecooler (24) for cooling the PCR chamber can be a structurally separateddevice with respect to the heater (23). In the exemplary embodiment ofFIG. 8, the cooler can be a small fan placed within a metal enclosureunderneath the sample polyimide chip. In other embodiments, the coolermay be placed elsewhere with respect to the sample polyimide chip, butin close proximity to the latter, as to provide efficient cooling byforcing air onto the sample polyimide chip. For the particular notedcase where the coil is on an FR-4 layer, cooling from underneath is notpossible as the FR-4 material is an excellent insulator. In this case,the fan may be placed above the sample polyimide and forcing air throughthe top of the sample. Alternatively, the embodiment of FIG. 8 may beused in the case where the coil is on an FR-4 based layer provided acutout is made in the FR-4 in the region of the chamber and the heatingcoil. It should be further noted that the cooler and the heater areopportunely used to set temperatures suitable for the PCR reactioncycle. The temperatures can be higher than room temperatures.

In addition, according to further aspects of the present disclosure andas depicted by FIGS. 8, 11 and 12, a PCR temperature controller (26)having a temperature sensing device (27) can be provided. The PCRtemperature controller (26) can be associated to the PCR chamber (15)for sensing and controlling the temperature in the PCR chamber.Temperature sensing may be performed using a multitude of methods. Forexample, the temperature sensing device can include a temperature sensorbonded directly, or located, onto the bottom of the PCR chamber asdepicted by FIG. 6, or alternatively the temperature sensor can bebonded directly, or located, onto a top portion of the PCR chamber (15)as depicted by FIG. 5. The temperature sensor used may be for example anMCP9701 low-power linear active thermistor manufactured by Microchip,and which provides an output voltage range of 500 mV at a 10 mV/Cresolution. It follows that the temperature sensing device (27) can beincluded within the circuit board (PCB) fluidic device (100).

According to alternative embodiments of the present disclosure asensitive resistance measurement circuit can be applied. The sensitiveresistance measurement circuit can use the temperature coefficient ofresistivity (TCR) of the copper coil (which forms the heater) beneaththe PCR chamber to measure the chamber temperature.

Because of the complexity of a control scheme, a microprocessor can beuseful for a PCR temperature controller. It follows that according tofurther aspects of the present disclosure, the PCR temperaturecontroller includes a microprocessor. FIG. 11 shows a portion of thecontrol circuitry wherein a microprocessor (U2) is used to implement thetemperature controller. In particular, pin 8 of U2 is used to control acurrent through the heater coil via a Darlington transistor (T1) whichhas high current capability, which current in turn causes heatdissipation through the coil underneath the chamber. A temperaturesensor at the vicinity of the chamber (FIGS. 5, 6) detects thetemperature and provides the microprocessor (U2) with a voltageproportional to the sensed temperature at pin 13 of U2.

With reference to FIG. 9 and FIG. 10, according to one embodiment of thepresent disclosure, the design, both in terms of hardware and software,can be optimized for the lowest possible cost. In particular, FIG. 10shows that the performance of a preliminary version of the controller,particularly for PCR-critical temperatures, can be sufficient for PCR.In terms of software, a fixed-point PID controller can be implemented toreduce processing power necessary in the microcontroller (e.g. as usedin current commercial systems), permitting the use of an extremely lowcost Microchip PICI6F/PICI2F series 8-bit microcontroller, which isshown in FIG. 11 (U2). This particular fixed point controller can employseveral components not common to most PID controllers (as it is shown inFIG. 9) to improve performance without requiring excessive processingpower and associated high cost.

Nonlinearity correction, actuator asymmetry correction, anti-windup, andlow pass filter are all additional features in the controller notpresent in canonical PID controller, all of which improve controlperformance with limited computational resources.

The optimized PID controller shown in FIG. 9 is used to control thetemperature of the chamber by minimizing the temperature error E(s)derived from the difference between the desired temperature, provided bythe Setpoint control input to the PID controller, and the measuredtemperature (370) obtained by the Measurement device. The skilled personmay appreciate the added features in the controller of FIG. 9 withrespect to a standard (canonical) PID controller which are now describedin further details. Going back to FIG. 9, the temperature error E(s) isfed to a modified PID Controller Block (300) comprising the threestandard processing units of a PID controller, the proportional unit(301) represented by a constant K_(p) function, the integral unit (302)represented by 1/T_(i)s function and the derivative unit (303)represented by T_(d)s function, where the constants K_(p), T_(i) andT_(d) are programmed values dependent on the input Setpoint. Each ofthese units provides a correction term based on the temperature errorE(s).

In the embodiment of FIG. 9, correction term from the differential unitis subjected to a low pass filter (310), thus controlling the rate ofchange which may be dictated by a relatively large swing in the errorcomponent, either by virtue of the limited resolution of the controlleror the requested Setpoint. Similarly, an Anti-Windup component (320) isprovided prior to feeding the error E(s) to the derivative unit (302),thus countering excessive overshoot of the controller in response tolarge swings in Setpoint that may be requested by the process. Theevaluated correction terms by each of the units are then summed tocreate a combined correction (330) out of the PID Controller Block(300). In order to adjust for further process limitations, additionalconditioning to the combined correction (330) is performed. Inparticular, in order to compensate for difference in process responsebetween ramping up (heating) and ramping down (cooling) the temperature,an Asymmetry correction unit (340), which function is dependent of theSetpoint, is added to the controller.

Finally, in order to compensate for the non-linear response of theactuator when driven at high gains (e.g. close to saturation), anActuator-saturation correction unit (350) is provided. The personskilled in the art will appreciate the added performance obtained bythese features and as evaluated by the heating/cooling curve of FIG. 10.It should be further noted that the results depicted by FIG. 10 areobtained by using forced-air cooling and resistive heating (coil). Theintegrated heater on the PCB fluidic device (100) is connected to thelines marked “VHEAT” and “VHEAT-” of FIG. 11. When the Darlingtontransistor (T1) is turned on, the heater element is connected to groundvia the transistor, thus causing current to flow from “VHEAT” powerterminal to ground through the heater (effectively the transistorcontrolling the current flow though the coil).

According to further aspects of the present disclosure, when activecooling is used, the temperature dynamics of the chip can differdepending on whether it is being cooled (or heated). A simple model ofheating/cooling can be Newton's law of cooling, which states that heattransfer can be proportional to the difference in temperature. In otherwords, the control dynamics of a purely passively cooled system areidentical under heating and cooling. From a control loop viewpoint, thiscan be a simple pole, at same location, for both passive cooling andheating. When active cooling is used, e.g. forced air from a fan, theproportionality constantly changes. This affects the location of thepole. When forced air is used when the chip is being cooled, but notheated, the control loop must account for this asymmetry. Since it canbe known whether the printed circuit board (PCB) fluidic device (100) isunder a heating phase or under a cooling phase, an asymmetry correctioninto the control system can be designed.

In addition it should be noted that, according to some aspects of thepresent disclosure, the use of software decimation techniquesadditionally permits increased resolution without increased circuitcomplexity and/or temperature sensor and other hardware cost.

It should be further noted that, according to some aspects of thepresent disclosure, because of the use of separate heating (copperheater) and cooling (fan) devices, usage of an H-bridge, which requiresfour high power transistors and more complex driver circuitry, can beavoided. Instead, only two fairly low cost transistors may be used, oneto drive the heater and one to drive the cooler.

It further follows that the apparatus according to the presentdisclosure can also implement a cost-optimized design for temperaturecontrol. Therefore, it appears that the apparatus of some embodiments ofthe present disclosure can be superior to conventional devices in termsof cost and complexity and with similar thermal performance.

The examples set forth above are provided to give those of ordinaryskill in the art a complete disclosure and description of how to makeand use the embodiments of the disclosure, and are not intended to limitthe scope of what the inventors regard as their disclosure.Modifications of the above-described modes for carrying out thedisclosure, including pressure control devices, accumulators, and soforth, may be used by persons of skill in the art, and are intended tobe within the scope of the following claims. All patents andpublications mentioned in the specification may be indicative of thelevels of skill of those skilled in the art to which the disclosurepertains. All references cited in this disclosure are incorporated byreference to the same extent as if each reference had been incorporatedby reference in its entirety individually.

It is to be understood that the disclosure is not limited to particularmethods or systems, which can, of course, vary. It is also to beunderstood that the terminology used herein is for the purpose ofdescribing particular embodiments only, and is not intended to belimiting. As used in this specification and the appended claims, thesingular forms “a,” “an,” and “the” include plural referents unless thecontent clearly dictates otherwise. The term “plurality” includes two ormore referents unless the content clearly dictates otherwise. Unlessdefined otherwise, all technical and scientific terms used herein havethe same meaning as commonly understood by one of ordinary skill in theart to which the disclosure pertains.

A number of embodiments of the disclosure have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the presentdisclosure. Accordingly, other embodiments are within the scope of thefollowing claims.

The invention claimed is:
 1. A printed circuit board (PCB), comprising:a Polymerase Chain Reaction (PCR) chamber for performing a PCR; aprinted circuit board (PCB) fluidic device, wherein the PCR chamber is afluidic chamber and is located in the printed circuit board (PCB)fluidic device.
 2. The printed circuit board (PCB) of claim 1, whereinthe printed circuit board (PCB) fluidic device includes a multilayerflex-on-rigid backing arrangement comprising flex layers.
 3. The printedcircuit board (PCB) of claim 2, wherein the PCR chamber is containedwithin the flex layers.
 4. The printed circuit board (PCB) of claim 3,wherein the flex layers are made of Kapton compatible with the PCR. 5.The printed circuit board (PCB) of claim 2, wherein a flame retardant 4(FR-4) based construction is located beneath the flex layers, the FR-4based construction containing electronic circuit board traces and aheater for heating the PCR chamber.
 6. The printed circuit board (PCB)of claim 5, wherein the heater comprises a trace coil.
 7. The printedcircuit board (PCB) of claim 6, wherein the trace coil comprises copper.8. The printed circuit board (PCB) of claim 5, wherein the electroniccircuit board traces comprise a PCR temperature controller configured tocontrol the heater.
 9. The printed circuit board (PCB) of claim 8,further comprising a temperature sensing device connected to thetemperature controller and associated with the PCR chamber such that thesensing device measures the temperature of the PCR chamber.
 10. Theprinted circuit board (PCB) of claim 8, wherein the heater comprises atrace coil and the temperature sensing device comprises a sensitiveresistance measurement circuit connected to the temperature controllerand to the trace coil.
 11. The printed circuit board (PCB) of claim 8,wherein the temperature controller comprises an anti-windup component.12. The printed circuit board (PCB) of claim 8, wherein the temperaturecontroller comprises a low pass filter.
 13. The printed circuit board(PCB) of claim 8, wherein the temperature controller comprises anasymmetry correction unit.
 14. The printed circuit board (PCB) of claim8, wherein the temperature controller comprises an actuator-saturationcorrection unit.